An electronic product such as a computer and a mobile terminal includes an electronic device such as a crystal unit, an oscillator, and a resonator. A piezoelectric device includes a piezoelectric vibrating piece vibrating at a predetermined frequency. As such piezoelectric vibrating piece, for example, there has been known a configuration that forms a pair of electrodes on a front surface and a back surface of an SC-cut crystal element (see Patent Document 1). An unwanted response (an A mode and a B mode) is excited at an SC-cut quartz-crystal vibrating piece, in addition to a main vibration (a C mode). To restrain the B mode, which is the unwanted response near the C mode, the main vibration, a filter or a similar member is necessary.